title: The nature of the background in radionuclide ventriculography: deductions from the mathematical behaviour of the ejection fraction.
abstract: The relationship between the ejection fractions calculated from 'uncorrected' radionuclide time activity curves (UEF) and angiographic ejection fractions (AEF) in 200 catheterized patients yielded the regression equation AEF = 1.74 UEF + 0.21. It follows from this linear relationship that the left ventricular ejection fraction can be estimated by linear regression without explicit background correction: RREF = 1.74 UEF + 0.21, where RREF is the radionuclide regression ejection fraction. We first investigated the possibility that changes in photon self-attenuation within the cardiac chambers cause the observed mathematical characteristics of the cardiac background, B. Self-attenuation was calculated for cylindrical and spherical ventricular models. The results were insensitive to the particular geometry and would have only a small effect on the observed EF. Alternatively, the 'background' may result from extra-ventricular radiation scattering from the heart into the detector. If we assume that B should be proportional to the ventricular scattering volume, Bd = Kd EDC for diastole and Bs = Ks ESC for systole, the background corrected ejection fraction will be BCEF = K UEF + (1-K) where K = (1-Ks)/(1-Kd). This agrees with the form of the empirical regression equation.
authors.affiliation: Thomas Jefferson University Hospital, Philadelphia, PA.
authors.forename: E J
authors.initials: EJ
authors.lastname: Gandsman
authors.forename: D L
authors.initials: DL
authors.lastname: North
authors.forename: E W
authors.initials: EW
authors.lastname: Bough
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D006801:Humans; D015233:Models, Statistical; D015635:Radionuclide Ventriculography / Q000706:statistics & numerical data*; D012044:Regression Analysis; D013318:Stroke Volume